0 in the middle is your current haste/mastery rating. Everything under the horizontal line is a DPS loss everything over it is a gain. Now just look where the highest peak is. It's at 1200 mastery to haste. So change gems, reforge, etc. to reduce your mastery by 1200 and add haste instead.

Rerun and narrow the amount/step values and adjust gear setup until you get something like this.